November 2009 — The APEX telescope

While ALMA is currently under construction, astronomers are already doing millimetre and submillimetre astronomy at Chajnantor, with the Atacama Pathfinder Experiment (APEX). This is a new technology 12-metre telescope, based on an ALMA proto-type antenna, and operating at the ALMA site. It has modified optics and improved antenna surface accuracy, and is designed to take advantage of the excellent sky transparency, working with light at wavelengths from 0.2–1.4 mm. The 5100-metre high site opens new atmospheric windows, allowing astronomers to observe molecules and atoms at wavelengths where previous ground-based telescopes were almost blind. Astronomers are using APEX to study the conditions inside molecular clouds, such as those around the Orion Nebula, and the Pillars of Creation in the Eagle Nebula. APEX is a collaboration between the Max-Planck- Institute for Radioastronomy (MPIfR), Onsala Space Observatory and ESO.